Crystal ball climate change

The Pentagon recently advised the US government that the biggest threat to America was climate change, not terrorism! With general consensus that the planet is getting hotter, the question has now become 'how hot, how soon, and with what consequences?'

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If you're like most people, when you listen to the evening weather report you think of it as more of a general guide rather than absolute fact. And if you think how hard it is to predict tomorrow or next week's weather, imagine being a climate scientist who's trying to predict the weather for the next decade or century.

Given the difficulties of long range weather forecasting, it's not surprising that there is disagreement in the scientific community when it comes to global warming. Some scientists don't believe there is enough evidence to suggest that global warming is happening, while others accept the Earth is getting hotter but attribute the temperature rise to natural phenomenon that is independent of human activities. However, the majority of climate scientists now agree that global warming is happening and it is caused by the human activity of burning fossil fuels for energy and transport.

Climate change is not new. A long term look at the Earth's climate over millions of years reveals a history of variation. The Earth has experienced hot, steamy periods and long cold Ice Ages. What is new is the speed at which we are heating up the planet.

In the last 100 years the temperature has increased by 0.6 degrees C. The Intergovernmental Panel on Climate Change (IPCC) predicts the planet will continue to warm by 1.4 to 5.8 degrees C by 2100 and the impacts will spread far and wide.

Hot and cold

Global warming implies that the whole Earth will simply get hotter, but it's more complex than that, with some places expected to cool down.

Climate change involves changes in temperature, rainfall, ocean currents, melting ice and anything and everything to do with the earth's climate. These changes will be different for everyone — depending on where you live, your livelihood and you and your country's ability to cope with the changes.

People living at high latitudes may benefit from global warming, warmer weather may boost agriculture and less harsh winters will be easier to live through.

A hotter Oz

However, in Australia, climate change will bring hotter weather. Australia's temperature is expected to increase more than the average global temperature rise with more days over 35 degrees C and fewer days below 0 degrees C expected.

For Australian residents, water shortages and loss of biodiversity have been identified as the biggest concern.

As the planet heats up more water will evaporate. Most of Australia will become drier while some areas in the northeast will be subject to more rain, which could lead to flooding.

Rising Sea levels

Australian coastal residents may also experience flooding from severe tides. And rising sea levels will be a problem — as the Earth heats up so will the oceans, and as water heats up it expands. The expansion of water will be the major reason sea levels will rise, with some contribution from melting ice at the poles.

Just as an ice block melts faster on a hot day, higher temperatures will lead to polar ice melting at a faster rate. Australian scientists studying Antarctic ice sheets and glaciers predict that global warming could break up the west Antarctic ice sheet, leading to more water melting from glaciers and increasing sea levels by 6 to 8 metres when it happens.

Considering the majority of the world's population live close to the coast, our cities may look more like Venice in the future. People living on low-lying Islands, such as the Maldives, could be literally washed from their homes with as little as a 0.5 m rise in sea levels, as predicted to occur by 2100.

Australia's favourite beaches may be underwater and surfers may have to move to different spots as rising sea levels re-shape the Australian coastline.

Ocean currents

Ocean currents will be affected by melting ice from the Antarctic and Arctic regions. Melting polar ice could slow down the thermohaline current (THC).

The THC is an ocean current caused by the movement of cold and salty water — which is denser than warmer fresh water — sinking deep into the ocean at the poles. The current works like a conveyor belt drawing warm surface water from the equator to replace the cold sinking water.

In the northern hemisphere, the THC draws warm gulf waters northwards along the coast of Europe. Winds, acting like a blow heater, then deliver the warmth from the water to the land.

Melting ice caps means more freshwater entering the ocean at the poles. Freshwater is not as dense as salt water and less water will sink in the Arctic region. It's the sinking water that drives the THC. Without the driving force, the THC could slow and UK and Europe would lose the warming effect of the gulf water flow giving the countries a serious chill.

Coral Reefs

Changes in atmospheric and ocean temperature as well as changes in weather can alter habitats and affect biodiversity. Coral reefs are particularly sensitive to changes in temperature and have been called the 'canaries' of climate change, after the practice of using the death of the birds to signal the presence of dangerous gases in coalmines.

Coral reefs not only support a huge range of fish species but a huge tourist industry as well. Climate change threatens coral reefs and we are already seeing the effects. The rise in seawater temperature kills algae that live on the coral and provide nutrients to the anemones, the soft squishy bits that inhabit the hard coral skeleton. Global warming, due to increased atmospheric carbon dioxide, increases the acidity of the seawater and stops the anemone secreting the coral skeleton. The overall effect is coral bleaching, where the live part of the coral dies, taking with it the colours that make the coral so beautiful.

Extreme weather & disease

Extreme weather is likely to increase the occurrence of typhoons, floods, mudslides, El Niño and other climate associated natural disasters.

Global warming is also expected to impact on human health by expanding geographical zones of tropical diseases such as malaria. In Africa, where many countries already struggle with health problems, the spread of diseases such as malaria is likely to occur. Malaria may become a problem in Australia, but because of better access to disease prevention programs and treatment, it's not expected to be as disastrous as in Africa.

What do we do?

Scientists can help people understand the consequences of climate change, says CSIRO climate scientist Roger Jones, but it's up to the world community to decide what change is acceptable and what temperature is too hot to handle.

It is now generally agreed that a one degree C rise in global temperature is inevitable. Some scientists and climate change prevention groups have suggested that a 2 degree C rise in global temperature would be 'dangerous' and the world should try and stop this from happening. But Australia remains uncommitted to defining a dangerous or maximum acceptable limit for climate change. Why? Because what's dangerous will be different for individuals, communities and countries, says Roger Jones from CSIRO, who doesn't believe current world governments would be able to reach a consensus.

Australia's economy relies heavily on coal and energy industries and the government must weigh up the impact of global warming with the economic impact of reducing these industries.